Expanding the Origin of Stereocontrol in Propene Polymerization Catalysis

Originally developed on heterogeneous Ziegler–Natta (ZN) catalysts, the model of “chiral growing chain conformation” developed by Corradini to explain the origin of stereocontrol in propene polymerization was extended to all stereoselective polymerization catalysts. The idea that the chiral recognition is performed by the site-chirality through the conformation of growing chain represents the “marker” of ZN toward, for example, asymmetric catalysis in which a chiral host molecule recognizes directly two enantiomeric guest molecules. In this paper, by using DFT calculations, we show that the origin of the stereocontrol for the new generation of Hf­(IV)-pyridylamido-based catalysts is somewhat different and more similar to the asymmetric catalysis.该手性增长链构象模型最初由科拉迪尼（Corradini）针对多相齐格勒-纳塔（Ziegler–Natta, ZN）催化剂开发，用于阐释丙烯聚合过程中立体调控的起源，后续被推广至所有立体选择性聚合催化剂体系。该模型提出，手性识别通过位点手性借助增长链的构象完成，这一观点也成为齐格勒-纳塔催化剂用于不对称催化（例如手性主体分子直接识别两种对映异构客体分子的催化体系）的标志性特征。本文通过密度泛函理论（DFT）计算证实，新一代铪(IV)-吡啶酰胺基催化剂的立体调控起源则存在显著差异，其催化机制更趋近于不对称催化模式。